After the considerable publicity attending the successful launch of the first International Earth Satellite, on April 26th, 1962, very little further information has been available to the general public. But the eventual fulfilment of its mission quickly became apparent at the special Discussion Meeting on the Ariel satellite, held at the Royal Society's apartments, Burlington House, on May 2nd and 3rd, 1963. I n his opening remarks, Sir Harrie Massey, chairman of the British National Committee on Space Research, congratulated the United Kingdom and United States scientists and engineers who had combined so happily on this venture. Throughout the two days Sir Harrie led discussion on the project in which he himself had played a leading part.